A designer synthetic chromosome fragment functions in moss

Here, we report the in vivo assembly of chromosomal fragments in the moss Physcomitrium patens, producing phenotypically virtually wild-type lines in which one-third of a chromosomal arm’s coding region is replaced by redesigned, chemically synthesized fragments. By eliminating 58.2% of the sequence, we significantly simplified the genome without discernible phenotypic effects, implying that most transposable elements minimally impact fitness. We also introduced other sequence modifications, such as PCRmark incorporation, gene locus swapping, and stop codon substitution. Despite these substantial changes, the complex epigenetic landscape was correctly reestablished, albeit with some three-dimensional conformation alterations. The synthesis of a partial multicellular eukaryotic chromosome arm lays the foundation for the synthetic moss genome project (SynMoss) and paves the way for genome synthesis in multicellular organisms.本研究报道了小立碗藓(Physcomitrium patens)体内染色体片段的组装工作，成功获得表型几乎与野生型一致的株系——该株系的一条染色体臂三分之一的编码区已被重新设计的化学合成片段所替换。通过删除58.2%的序列，我们在未引发可检测表型效应的前提下大幅简化了该基因组，这表明大多数转座因子对生物体适合度的影响极小。本研究同时引入了多项其他序列修饰手段，例如PCR标记（PCRmark）嵌入、基因座交换以及终止密码子替换。尽管存在上述显著改造，复杂的表观遗传景观仍得以正确重建，仅伴随少量三维构象变化。部分多细胞真核生物染色体臂的合成为合成苔藓基因组计划（SynMoss）奠定了基础，同时也为多细胞生物的基因组合成研究铺平了道路。